Update cheatsheet.fr.md

12.temporary_ins/90.electromagnetism-in-vacuum/30.maxwell-electromagnetism-potentials/cheatsheet.fr.md

@@ -112,6 +112,25 @@ RÉSUMÉ
 
 --------------->
 
+$`div\,\overrightarrow{B} = 0\quad`$ (Maxwell-Flux)
+
+ $`\color{blue}{\scriptsize{\left.\begin{align} \quad\quad &div\,\overrightarrow{B} = 0\\
+                     &div\,\overrightarrow{U}=0\quad\Longleftrightarrow\quad\exist\overrightarrow{V}\,,\, \overrightarrow{U}=\overrightarrow{rot}\,\overrightarrow{V}\end{align}
+               \right\}\Longrightarrow\\
+        \exists\overrightarrow{A}\,,\, \overrightarrow{B}=\overrightarrow{rot}\,\overrightarrow{A}}}`$  
+
+<!-------------
+ $`\color{blue}{\scriptsize{\left.\begin{align} \quad\quad &cos(a+b)=cos(a)cos(b)-sin(a)sin(b)\\
+                     &cos(a-b)=cos(a)cos(b)+sin(a)sin(b)\end{align}
+               \right\}\Longrightarrow\\
+        \quad\quad cos^2(a)=cos(a)cos(a)=\dfrac{1}{2}[cos(a+a)+cos(a-a)]\\
+        \quad\quad\quad\quad=\dfrac{1}{2}[1 + cos(2a)]}}`$    
+-------------->
+        
+     $`\overrightarrow{rot}\,\overrightarrow{U}=\overrightarrow{0}\quad\Longleftrightarrow\quad\exists\phi\,,\, \overrightarrow{U}=\overrightarrow{grad}\,\phi`$
+        
+ $`div\,\overrightarrow{U}=0\quad\Longleftrightarrow\quad\exists\phi\,,\, \overrightarrow{U}=\overrightarrow{rot}\,\overrightarrow{V}`$
+
 $`\overrightarrow{rot}\,\overrightarrow{E}=-\dfrac{\partial \overrightarrow{B}}{\partial t}
 =-\dfrac{\partial \big(\overrightarrow{rot}\,\overrightarrow{A}\big)}{\partial t}
 =-\overrightarrow{rot}\,\dfrac{\partial \overrightarrow{A}}{\partial t}`$